Inverter control method and device, frequency converter, motor, medium and product

Abstract

The invention discloses an inverter control method and device, a frequency converter, a motor, a storage medium and a computer program product, and the method comprises the steps: obtaining the three-phase current of the motor under the operation condition of the motor; according to the three-phase current of the motor, determining a frequency interval to which the operation frequency of the motor belongs in a set frequency range; determining the polarity of the three-phase current of the motor according to the frequency interval to which the operation frequency of the motor belongs in a set frequency range; and according to the polarity of the three-phase current of the motor, adjusting the conduction time of a switch tube of an upper bridge arm and the conduction time of a switch tube of a lower bridge arm of each phase of bridge arm in three-phase bridge arms of an inverter of the motor so as to carry out dead zone compensation on the inverter of the motor. According to the scheme, the current polarity is judged on the basis of vector control, the dead zone effect is compensated according to the current polarity, and the accuracy and reliability of dead zone effect compensation of the inverter are guaranteed.

Description

Technical Field

[0001] The present invention belongs to the field of motor control technology, and specifically relates to a control method, device, frequency converter, motor, storage medium and computer program product of an inverter, and more particularly to a dead zone compensation method, device, frequency converter, motor, storage medium and computer program product for an inverter. Background Art

[0002] In the two-level voltage source inverter of the motor, each phase controls the voltage output through the on and off of the power switch tube. In order to avoid the upper and lower switches of the same phase being directly turned on and causing damage to the device, it is necessary to insert a delay opening time into the control pulse of the switch tube to allow a safety margin for the upper and lower tubes to be turned on and off. The inserted delay time is called the dead time. During the dead time, neither the upper nor lower tubes are turned on, and the freewheeling diode on the bridge arm is used for freewheeling. In the freewheeling stage, the output voltage limit is determined by the output current polarity rather than the switching command, which causes the output current to be distorted. The current distortion caused by the dead time is called the dead time effect. The dead time effect of the inverter will cause problems such as torque pulsation, current distortion, and noise in the motor, affecting the reliability of the motor operation.

[0003] The above contents are only used to assist in understanding the technical solution of the present invention and do not constitute an admission that the above contents are prior art. Summary of the invention

[0004] The object of the present invention is to provide a control method, device, frequency converter and motor, storage medium and computer program product of an inverter to solve the dead zone effect of the inverter, which will cause problems such as torque pulsation, current distortion, noise, etc. of the motor, affecting the reliability of the motor operation, and to achieve the effect of ensuring the accuracy and reliability of the dead zone effect compensation of the inverter by judging the current polarity on the basis of vector control and compensating for the dead zone effect according to the current polarity.

[0005] The present invention provides a control method for an inverter, the inverter comprising: a three-phase bridge arm; each phase bridge arm in the three-phase bridge arm comprises: a switch tube of an upper bridge arm and a switch tube of a lower bridge arm; the midpoint of each phase bridge arm is connected to a winding of a corresponding phase in a three-phase winding of a motor; the control method for the inverter comprises: when the motor is running, obtaining the three-phase current of the motor; determining the frequency interval to which the operating frequency of the motor belongs within a set frequency range according to the three-phase current of the motor; determining the polarity of the three-phase current of the motor according to the frequency interval to which the operating frequency of the motor belongs within the set frequency range;

[0006] According to the polarity of the three-phase current of the motor, the conduction time of the switch tube of the upper bridge arm and the conduction time of the switch tube of the lower bridge arm of each phase bridge arm in the three-phase bridge arm are adjusted to compensate the dead zone of the inverter.

[0007] In some embodiments, a frequency range is set, including: a first frequency interval and a second frequency interval, the upper limit of the first frequency interval is less than the lower limit of the second frequency interval; based on the three-phase current of the motor, the frequency interval to which the operating frequency of the motor belongs within the set frequency range is determined, including: for any phase current of the three-phase current of the motor, determining whether the any phase current is less than a preset current threshold; if it is determined that the any phase current is less than the preset current threshold, determining that the operating frequency of the motor is in the first frequency interval; if it is determined that the any phase current is greater than or equal to the preset current threshold, determining that the operating frequency of the motor is in the second frequency interval.

[0008] In some embodiments, a frequency range is set, including: a first frequency interval and a second frequency interval, the upper limit of the first frequency interval is less than the lower limit of the second frequency interval; the polarity of the three-phase current of the motor is determined according to the frequency interval to which the operating frequency of the motor belongs within the set frequency range, including: if the operating frequency of the motor is in the first frequency interval, the three-phase current of the motor is subjected to coordinate transformation and filtering processing to obtain a first processed value of the three-phase current of the motor; then, the polarity of the three-phase current of the motor is determined according to the first processed value of the three-phase current of the motor; if the operating frequency of the motor is in the second frequency interval, the polarity of the three-phase current of the motor is determined according to the current value of the three-phase current of the motor; or, the three-phase current of the motor is subjected to filtering processing to obtain a second processed value of the three-phase current of the motor; then, the polarity of the three-phase current of the motor is determined according to the second processed value of the three-phase current of the motor.

[0009] In some embodiments, after coordinate transformation and filtering processing are performed on the three-phase current of the motor, a first processed value of the three-phase current of the motor is obtained, including: for the three-phase current of the motor, the abc coordinate system is converted to the αβ coordinate system, and then converted to the dq coordinate system; filtering processing is performed in the dq coordinate system, and then inverse transformation is performed to restore it to the abc coordinate system to obtain the first processed value of the three-phase current of the motor.

[0010] In some embodiments, the polarity of the three-phase current of the motor is determined according to the first processed value of the three-phase current of the motor, including: for the first processed value of any phase current among the first processed values ​​of the three-phase current of the motor, determining whether the first processed value of the any phase current is greater than 0: if so, determining that the current polarity of any phase current of the three-phase current of the motor is positive; otherwise, determining that the current polarity of any phase current of the three-phase current of the motor is negative; and / or, according to the current value of the three-phase current of the motor, the polarity of the three-phase current of the motor is determined, including: for the current value of any phase current among the current value of the three-phase current of the motor, determining Whether the current value of any phase current is greater than 0: if so, determine that the current polarity of any phase current of the three-phase current of the motor is positive, otherwise, determine that the current polarity of any phase current of the three-phase current of the motor is negative; and / or, determine the polarity of the three-phase current of the motor according to the second processed value of the three-phase current of the motor, including: for the second processed value of any phase current in the second processed value of the three-phase current of the motor, determine whether the second processed value of any phase current is greater than 0: if so, determine that the current polarity of any phase current of the three-phase current of the motor is positive, otherwise, determine that the current polarity of any phase current of the three-phase current of the motor is negative.

[0011] In some embodiments, the polarity of the three-phase current of the motor includes: the current polarity of any phase current of the three-phase current of the motor is positive, or the current polarity of any phase current of the three-phase current of the motor is negative; according to the polarity of the three-phase current of the motor, the conduction time of the switch tube of the upper bridge arm of each phase bridge arm in the three-phase bridge arm and the conduction time of the switch tube of the lower bridge arm are adjusted to compensate for the dead zone of the inverter, including: for any phase current of the three-phase current of the motor, if the current polarity of any phase current is positive, then for the inverter corresponding to the phase current, the conduction time of the switch tube of the upper bridge arm of each phase bridge arm in the three-phase bridge arm is adjusted to compensate for the dead zone of the inverter, including: for any phase current of the three-phase current of the motor, if the current polarity of any phase current is positive, then for the inverter corresponding to the phase current, the conduction time of the switch tube of the lower bridge arm is adjusted to compensate for the dead zone of the inverter, For any phase bridge arm corresponding to any phase current, the conduction time of the switch tube of the upper bridge arm in the any phase bridge arm is extended by a set time, and the conduction time of the switch tube of the lower bridge arm in the any phase bridge arm is shortened by a set time; for any phase current among the three-phase currents of the motor, if the current polarity of any phase current is negative, then for any phase bridge arm in the inverter corresponding to the any phase current, the conduction time of the switch tube of the upper bridge arm in the any phase bridge arm is shortened by a set time, and the conduction time of the switch tube of the lower bridge arm in the any phase bridge arm is extended by a set time.

[0012] Matching the above method, the present invention provides a control device for an inverter on the other hand, the inverter comprising: a three-phase bridge arm; each phase bridge arm in the three-phase bridge arm comprises: a switch tube of an upper bridge arm and a switch tube of a lower bridge arm; the midpoint of each phase bridge arm is connected to the winding of the corresponding phase in the three-phase winding of the motor; the control device for the inverter comprises: an acquisition unit configured to acquire the three-phase current of the motor when the motor is running; a control unit configured to determine the frequency interval to which the operating frequency of the motor belongs within a set frequency range according to the three-phase current of the motor; the control unit is further configured to determine the polarity of the three-phase current of the motor according to the frequency interval to which the operating frequency of the motor belongs within the set frequency range; the control unit is further configured to adjust the conduction time of the switch tube of the upper bridge arm and the conduction time of the switch tube of the lower bridge arm of each phase bridge arm in the three-phase bridge arm according to the polarity of the three-phase current of the motor, so as to compensate the dead zone of the inverter.

[0013] In some embodiments, a frequency range is set, including: a first frequency interval and a second frequency interval, the upper limit of the first frequency interval is less than the lower limit of the second frequency interval; the control unit determines, based on the three-phase current of the motor, the frequency interval to which the operating frequency of the motor belongs within the set frequency range, including: for any phase current of the three-phase current of the motor, determining whether the any phase current is less than a preset current threshold; if it is determined that the any phase current is less than the preset current threshold, determining that the operating frequency of the motor is in the first frequency interval; if it is determined that the any phase current is greater than or equal to the preset current threshold, determining that the operating frequency of the motor is in the second frequency interval.

[0014] In some embodiments, a frequency range is set, including: a first frequency interval and a second frequency interval, the upper limit of the first frequency interval is less than the lower limit of the second frequency interval; the control unit determines the polarity of the three-phase current of the motor according to the frequency interval to which the operating frequency of the motor belongs within the set frequency range, including: if the operating frequency of the motor is in the first frequency interval, the three-phase current of the motor is subjected to coordinate transformation and filtering processing to obtain a first processed value of the three-phase current of the motor; then, the polarity of the three-phase current of the motor is determined according to the first processed value of the three-phase current of the motor; if the operating frequency of the motor is in the second frequency interval, the polarity of the three-phase current of the motor is determined according to the current value of the three-phase current of the motor; or, the three-phase current of the motor is subjected to filtering processing to obtain a second processed value of the three-phase current of the motor; then, the polarity of the three-phase current of the motor is determined according to the second processed value of the three-phase current of the motor.

[0015] In some embodiments, the control unit obtains a first processed value of the three-phase current of the motor after performing coordinate transformation and filtering processing on the three-phase current of the motor, including: converting the three-phase current of the motor from the abc coordinate system to the αβ coordinate system, and then converting it to the dq coordinate system; performing filtering processing in the dq coordinate system, and then inversely transforming and restoring it to the abc coordinate system to obtain the first processed value of the three-phase current of the motor.

[0016] In some embodiments, the control unit determines the polarity of the three-phase current of the motor according to the first processed value of the three-phase current of the motor, including: for the first processed value of any phase current among the first processed values ​​of the three-phase current of the motor, determining whether the first processed value of the any phase current is greater than 0: if so, determining that the current polarity of any phase current of the three-phase current of the motor is positive; otherwise, determining that the current polarity of any phase current of the three-phase current of the motor is negative; and / or, the control unit determines the polarity of the three-phase current of the motor according to the current value of the three-phase current of the motor, including: for the current polarity of any phase current among the current value of the three-phase current of the motor value, determine whether the current value of any phase current is greater than 0: if so, determine that the current polarity of any phase current of the three-phase current of the motor is positive, otherwise, determine that the current polarity of any phase current of the three-phase current of the motor is negative; and / or, the control unit determines the polarity of the three-phase current of the motor according to the second processed value of the three-phase current of the motor, including: for the second processed value of any phase current in the second processed value of the three-phase current of the motor, determine whether the second processed value of any phase current is greater than 0: if so, determine that the current polarity of any phase current of the three-phase current of the motor is positive, otherwise, determine that the current polarity of any phase current of the three-phase current of the motor is negative.

[0017] In some embodiments, the polarity of the three-phase current of the motor includes: the current polarity of any phase current of the three-phase current of the motor is positive, or the current polarity of any phase current of the three-phase current of the motor is negative; the control unit adjusts the conduction time of the switch tube of the upper bridge arm of each phase bridge arm in the three-phase bridge arm and the conduction time of the switch tube of the lower bridge arm according to the polarity of the three-phase current of the motor to perform dead zone compensation for the inverter, including: for any phase current of the three-phase current of the motor, if the current polarity of any phase current is positive, then for the inverter For any phase bridge arm in the inverter corresponding to any phase current, the conduction time of the switch tube of the upper bridge arm in the any phase bridge arm is extended by a set time, and the conduction time of the switch tube of the lower bridge arm in the any phase bridge arm is shortened by a set time; for any phase current among the three-phase currents of the motor, if the current polarity of any phase current is negative, then for any phase bridge arm in the inverter corresponding to any phase current, the conduction time of the switch tube of the upper bridge arm in the any phase bridge arm is shortened by a set time, and the conduction time of the switch tube of the lower bridge arm in the any phase bridge arm is extended by a set time.

[0018] Matching the above device, the present invention further provides a frequency converter, including: the control device of the inverter described above.

[0019] Matching the above-mentioned device, the present invention provides a motor on another aspect, including: the control device of the inverter mentioned above, or the frequency converter mentioned above.

[0020] In accordance with the above method, the present invention provides a storage medium on another aspect, wherein the storage medium includes a stored program, wherein when the program is executed, the device where the storage medium is located is controlled to execute the steps of the inverter control method described above.

[0021] Matching the above method, the present invention further provides a computer program product on the other hand, including a computer program, which implements the steps of the inverter control method described above when executed by a processor.

[0022] Therefore, the scheme of the present invention, for the dead zone compensation of the three-phase full-bridge inverter in the frequency converter of the motor, adopts the three-phase current of the motor, determines whether the motor is running at low frequency and light load or medium and high frequency and heavy load according to the three-phase current of the motor, and when the motor is running at low frequency and light load, the three-phase current of the motor is transformed and the current polarity is judged, and when the motor is running at medium and high frequency and heavy load, the polarity is judged according to the three-phase current of the motor, and according to the polarity of a phase current in the determined three-phase current, the conduction time of the upper and lower switch tubes of a phase bridge arm in the three-phase full-bridge inverter corresponding to the phase current is extended or shortened to realize the compensation of the dead time of certain bridge arms; thereby, by judging the current polarity on the basis of vector control and compensating for the dead zone effect according to the current polarity, the accuracy and reliability of the dead zone effect compensation of the inverter are guaranteed.

[0023] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention.

[0024] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic flow chart of an inverter control method according to an embodiment of the present invention;

[0026] Figure 2 A schematic flow chart of an embodiment of determining the frequency interval to which the operating frequency of the motor belongs within a set frequency range in the method of the present invention;

[0027] Figure 3 It is a flow chart of an embodiment of the method of the present invention for performing coordinate transformation and filtering on the three-phase current of the motor;

[0028] Figure 4 is a structural schematic diagram of an embodiment of a control device for an inverter of the present invention;

[0029] Figure 5 A schematic diagram of a flow chart of a method for inverter dead zone compensation according to the present invention;

[0030] Figure 6 It is a structural diagram of the inverter and the motor;

[0031] Figure 7 A schematic diagram of the current flow between the inverter and one phase (such as phase A) of the motor;

[0032] Figure 8 It is a schematic diagram of a current waveform of one phase (such as phase B) of the motor and a curve showing changes of its polarity over time;

[0033] Fig. 9Schematic diagram of curves of ideal switching and actual switching signals of a bridge arm of the inverter (such as a bridge arm formed by the switch S1 and the switch S4 ).

[0034] In conjunction with the accompanying drawings, the reference numerals in the embodiments of the present invention are as follows:

[0035] 102 - acquisition unit; 104 - control unit 104 . DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0037] Considering that the dead zone effect of the inverter will bring about problems such as torque pulsation, current distortion, and noise of the motor, it affects the reliability of the motor operation. Specifically, the distorted voltage pulses generated by the dead zone effect of the inverter will cause the voltage amplitude and phase to be distorted at the same time, thereby introducing current harmonics and causing motor torque pulsation, and the dead zone effect needs to be compensated. When the motor runs at low speed, the effective action time of the voltage vector is often short, and the dead zone effect is more prominent. Therefore, when the motor runs in the zero current area, the motor phase voltage will be dominated by the dead zone error voltage. At this time, the phase voltage is clamped to the no-load back electromotive force value of the phase motor, which will keep the zero-crossing phase current at around zero current until the effective voltage action time is greater than the actual current in the dead zone to get rid of the clamping state. This phenomenon is called zero current clamping phenomenon.

[0038] The zero current clamping phenomenon will cause serious distortion of the voltage synthesis vector, causing the other phase currents to be distorted as well. Therefore, the dead zone effect is often more serious when the motor is running at low speed. During the zero current clamping period, the polarity of the zero-passing phase current will change many times due to the freewheeling phenomenon of the dead zone effect, and the current contains high-order harmonics. If the polarity is directly judged based on the current and the dead zone voltage is compensated, the zero current clamping will lead to inaccurate compensation. The miscompensated voltage will make the dead zone effect in the zero current area more serious. Among them, the current amplitude is small and the harmonic content is high during low-frequency operation, the sinusoidal degree is not high, and there is an error in the current polarity detection, which affects the compensation time.

[0039] Therefore, the scheme of the present invention proposes a control method for an inverter, specifically a method for compensating for the inverter dead zone, which performs compensation according to the current polarity, sets a threshold segmented compensation according to the size of the feedback current, improves the torque pulsation, current distortion, noise and other problems caused by the inverter dead zone effect, and improves the reliability of the motor operation.

[0040] According to an embodiment of the present invention, a control method for an inverter is provided. Figure 1 The flow chart of an embodiment of the method of the present invention is shown. The inverter comprises: a three-phase bridge arm; each bridge arm of the three-phase bridge arm comprises: a switch tube of an upper bridge arm and a switch tube of a lower bridge arm; the midpoint of each bridge arm is connected to the winding of the corresponding phase in the three-phase winding of the motor. Figure 6 Figure 1 is a schematic diagram of the structure of the inverter and the motor. Figure 6 As shown, the structure of the inverter and the motor includes: capacitor C1, capacitor C2, switch tube S1, freewheeling diode D1 of switch tube S1, switch tube S2, freewheeling diode D2 of switch tube S2, switch tube S3, freewheeling diode D3 of switch tube S3, switch tube S4, freewheeling diode D4 of switch tube S4, switch tube S5, freewheeling diode D5 of switch tube S5, switch tube S6, freewheeling diode D6 of switch tube S6, and three-phase winding of motor MO. The collector of the switch tube S1 is connected to the cathode of the diode D1, and the emitter of the switch tube S1 is connected to the anode of the diode D1; the collector of the switch tube S2 is connected to the cathode of the diode D2, and the emitter of the switch tube S2 is connected to the anode of the diode D2; the collector of the switch tube S3 is connected to the cathode of the diode D3, and the emitter of the switch tube S3 is connected to the anode of the diode D3; the collector of the switch tube S4 is connected to the cathode of the diode D4, and the emitter of the switch tube S4 is connected to the anode of the diode D4; the collector of the switch tube S5 is connected to the cathode of the diode D5, and the emitter of the switch tube S5 is connected to the anode of the diode D5; the collector of the switch tube S6 is connected to the cathode of the diode D6, and the emitter of the switch tube S6 is connected to the anode of the diode D6. Among them, the positive end of the DC bus voltage Udc is respectively connected to the positive electrode of capacitor C1, the collector of switch tube S1, the collector of switch tube S3, and the collector of switch tube S5; the negative electrode of capacitor C1 is connected to the positive electrode of capacitor C2 and both are grounded (i.e., connected to the zero point). The negative end of the DC bus voltage Udc is connected to the negative electrode of capacitor C2, the emitter of switch tube S4, the emitter of switch tube S6, and the emitter of switch tube S2. The emitter of switch tube S1 is connected to the collector of switch tube S4, and is connected to the first phase (such as phase A) of the three-phase winding of the motor; the emitter of switch tube S3 is connected to the collector of switch tube S6, and is connected to the second phase (such as phase B) of the three-phase winding of the motor; the emitter of switch tube S5 is connected to the collector of switch tube S2, and is connected to the third phase (such as phase C) of the three-phase winding of the motor.

[0041] In the scheme of the present invention, Figure 1 As shown, the inverter control method includes: step S110 to step S140.

[0042] In step S110 , when the motor is running, the three-phase current of the motor is acquired.

[0043] In step S120, the frequency interval to which the operating frequency of the motor belongs within a set frequency range is determined according to the three-phase current of the motor.

[0044] In some embodiments, the set frequency range includes: a first frequency interval and a second frequency interval, the upper limit of the first frequency interval is less than the lower limit of the second frequency interval, the first frequency interval is such as a low-frequency light-load interval, and the second frequency interval is such as a medium-high frequency heavy-load interval. For the specific process of determining the frequency interval to which the operating frequency of the motor belongs within the set frequency range according to the three-phase current of the motor in step S120, see the following exemplary description.

[0045] Combine the following Figure 2 The flowchart of an embodiment of determining the frequency interval to which the operating frequency of the motor belongs within the set frequency range in the method of the present invention is shown, which further illustrates the specific process of determining the frequency interval to which the operating frequency of the motor belongs within the set frequency range in step S120, including: steps S210 to S230.

[0046] Step S210, for any phase current of the three-phase current of the motor, determine whether the any phase current is less than a preset current threshold, wherein any phase current of the three-phase current of the motor, such as the sampled current i_samp; preset current threshold, such as the current threshold i_threshold.

[0047] Step S220: If it is determined that any phase current is less than a preset current threshold, the operating frequency of the motor is determined to be in a first frequency interval.

[0048] Step S230: If it is determined that any phase current is greater than or equal to a preset current threshold, the operating frequency of the motor is determined to be in a second frequency range.

[0049] Figure 5 FIG. 1 is a flow chart of a method for inverter dead zone compensation according to the present invention. Figure 5 As shown, a method for inverter dead zone compensation includes:

[0050] Step 1, obtain the three-phase current of the motor as the sampling current i_samp; the sampling current first performs a preset value judgment, that is, judges whether the sampling current i_samp<current threshold i_threshold: if so, execute step 2, otherwise execute step 3.

[0051] Step 2: When the sampling current i_samp<current threshold i_threshold, that is, when the motor is running at low frequency and light load, step 21 is executed, that is, the polarity is determined by coordinate transformation, and then dead zone compensation is performed.

[0052] Step 3: When the sampling current i_samp≥current threshold i_threshold is satisfied, that is, when the motor is running at a medium or high frequency, step 31 is executed, that is, the sampling current can be directly used to determine the polarity, and then dead zone compensation is performed.

[0053] In the scheme of the present invention, dead zone compensation is performed on the basis of coordinate transformation, and the dead zone compensation is processed in segments according to the current size. When the current is small, the main component of the current is used to judge the polarity, and after the current becomes larger, the measured current is directly used to judge the polarity. This segmented processing well solves the problems of zero point clamping and complex large current calculation when judging the polarity of small currents, improves the accuracy of current polarity judgment, and ensures the accuracy and reliability of dead zone effect compensation for the inverter.

[0054] In step S130, the polarity of the three-phase current of the motor is determined according to the frequency interval to which the operating frequency of the motor belongs within the set frequency range.

[0055] In some embodiments, the frequency range is set to include: a first frequency interval and a second frequency interval, the upper limit of the first frequency interval is less than the lower limit of the second frequency interval, the first frequency interval is such as a low-frequency light-load interval, and the second frequency interval is such as a medium-high frequency heavy-load interval. In step S130, the polarity of the three-phase current of the motor is determined according to the frequency interval to which the operating frequency of the motor belongs within the set frequency range, including any of the following polarity determination situations:

[0056] The first polarity determination scenario: if the operating frequency of the motor is in the first frequency range, the three-phase current of the motor is subjected to coordinate transformation and filtering to obtain a first processed value of the three-phase current of the motor; then, the polarity of the three-phase current of the motor is determined based on the first processed value of the three-phase current of the motor.

[0057] In some implementations, the specific process of obtaining the first processed value of the three-phase current of the motor after coordinate transformation and filtering are performed on the three-phase current of the motor in step S130 is described in the following exemplary embodiments.

[0058] Combine the following Figure 3 The flowchart of an embodiment of the method of the present invention for coordinate transformation and filtering of the three-phase current of the motor further illustrates the specific process of coordinate transformation and filtering of the three-phase current of the motor in step S130, including: step S310 to step S320.

[0059] Step S310, converting the three-phase current of the motor from the abc coordinate system to the αβ coordinate system, and then to the dq coordinate system.

[0060] Step S320, performing filtering processing in the dq coordinate system, and then performing inverse transformation to restore to the abc coordinate system, to obtain a first processed value of the three-phase current of the motor.

[0061] like Figure 5 As shown, the method for inverter dead zone compensation also includes: step 21, considering that when the motor runs at low frequency and light load, the current is small and due to the influence of zero point clamping, the current directly sampled is not an ideal sinusoidal current. According to Fourier analysis, the current directly sampled is composed of fundamental component and harmonic component. If the current polarity is directly judged by the sampled current, it will cause polarity deviation and cannot improve the current distortion caused by the inverter dead zone effect; and directly using the sampled current for sector judgment will also bring errors to the sector judgment. For this reason, most methods are to directly filter the sampled current, but this will cause errors in the amplitude and phase of the sampled current. If the fundamental and harmonic waves of the sampled current are separated, the accuracy will be improved by using the fundamental wave containing the main information for processing.

[0062] Therefore, the solution of the present invention adopts this decomposition idea, performs forward transformation on the three-phase current, filters the three-phase current in the dq coordinate system, restores the three-phase current by reverse transformation, and then executes step 4 to perform dead zone compensation.

[0063] Specifically, in step 21, the sampled current is first transformed from the abc coordinate system to the two-phase stationary coordinate system αβ, and then to the dq coordinate system. a 、i b 、i c In the abc coordinate system and the αβ coordinate system, it is expressed as AC, but when converted to the dq coordinate system, the corresponding variable is expressed as DC. The DC filtering process will not affect its amplitude and phase. The original current converted to the dq coordinate system contains the fundamental component and harmonic component of the original current signal, which can be expressed as follows (1):

[0064]

[0065] Among them, i bd 、i bq It is the DC component in the synchronously rotating dq coordinate system, which is obtained by converting the fundamental wave component in the abc coordinate system. hd 、i hqIt is the high-order harmonic component in the synchronously rotating dq coordinate system, which is obtained by converting the high-frequency component in the abc coordinate system. d , q-axis current i q Filtering is performed to remove the high-frequency components in the current signal. The filtered current is the DC component obtained by converting the fundamental component of the original current, which contains the main components of the original current. The filtered DC component is then restored to the abc coordinate system through inverse transformation using equations (2) and (3), where θ is i bd and i A The angle between the αβ coordinate system and the dq coordinate system is used to determine the motor current polarity under the abc coordinate system. The accuracy of the current polarity determination is improved by determining the current polarity through coordinate transformation. Compared with directly filtering the sampled current, the current polarity determination through coordinate transformation converts the current to a DC state for filtering. The DC component will not change its amplitude and phase through filtering, which greatly improves the accuracy of the current polarity determination.

[0066]

[0067] The three-phase current obtained by transforming equations (2) and (3) is:

[0068]

[0069] Among them, i α is the α-axis current, i β is the β-axis current. Afterwards, the polarity of the current converted to the abc coordinate system is determined.

[0070] In the scheme of the present invention, when the motor is at low frequency, light load and small current, due to the existence of zero-crossing clamping, filtering the converted DC will not change the amplitude and phase of the original signal. The filtered current is inversely transformed and restored to the original. The restored signal reduces high-frequency interference and retains useful components compared to the original signal. Compared with directly judging the sampled current, this method improves the accuracy of filtering out interference and greatly improves the accuracy of current polarity judgment.

[0071] In some embodiments, the polarity of the three-phase current of the motor is determined based on the first processed value of the three-phase current of the motor, including: for the first processed value of any phase current among the first processed values ​​of the three-phase current of the motor, determining whether the first processed value of the any phase current is greater than 0: if so, determining that the current polarity of any phase current of the three-phase current of the motor is positive; otherwise, determining that the current polarity of any phase current of the three-phase current of the motor is negative.

[0072] like Figure 5As shown, the method for inverter dead zone compensation also includes: in step 21, the polarity of the current converted to the abc coordinate system is judged, and it is defined that when the current is greater than 0, the current polarity at this time is represented as a high level, that is, the current is positive; when the current is equal to 0, the current polarity is negative. The relationship between the current waveform of a phase of the motor and its polarity change over time can be seen in Figure 8 The example shown, Figure 8 It is a schematic diagram of a curve showing the current waveform of one phase (such as phase B) of the motor and its polarity changing with time.

[0073] In the scheme of the present invention, when the motor is at low frequency, light load and small current, the current polarity is judged by using the zero crossing point of the sinusoidal current after conversion, thereby improving the accuracy of the current polarity judgment and reducing interference, and ensuring that the dead zone compensation is accurate and reliable.

[0074] The second polarity determination scenario: if the operating frequency of the motor is in the second frequency range, the polarity of the three-phase current of the motor is determined according to the current value of the three-phase current of the motor; or, the three-phase current of the motor is filtered to obtain a second processed value of the three-phase current of the motor; then, the polarity of the three-phase current of the motor is determined according to the second processed value of the three-phase current of the motor.

[0075] In the scheme of the present invention, when the motor is at low frequency, light load and small current, due to the existence of zero-crossing clamping, filtering the converted DC will not change the amplitude and phase of the original signal. The filtered current is reversely transformed and restored to the original. Compared with the original signal, the restored signal reduces high-frequency interference and retains useful components. Compared with directly judging the sampled current, this method improves the accuracy of filtering out interference; when the motor is at medium and high frequency, heavy load and large current, there is no zero-crossing clamping, and the sampled current does not need to be transformed, and the polarity of the sampled current can be directly judged, reducing the complexity of large current polarity judgment and improving the real-time performance of polarity judgment.

[0076] In the solution of the present invention, the current signal can be filtered at any stage of the current, which can improve the accuracy of polarity judgment and better achieve dead zone compensation; the cutoff frequency of the filter can be determined according to the actual loop bandwidth.

[0077] In some embodiments, the polarity of the three-phase current of the motor is determined according to the current value of the three-phase current of the motor, including: determining whether the current value of any phase current among the current values ​​of the three-phase current of the motor is greater than 0: if so, determining that the current polarity of any phase current of the three-phase current of the motor is positive; otherwise, determining that the current polarity of any phase current of the three-phase current of the motor is negative.

[0078] Alternatively, the polarity of the three-phase current of the motor is determined based on the second processed value of the three-phase current of the motor, including: for the second processed value of any phase current among the second processed values ​​of the three-phase current of the motor, determining whether the second processed value of the any phase current is greater than 0: if so, determining that the current polarity of any phase current of the three-phase current of the motor is positive; otherwise, determining that the current polarity of any phase current of the three-phase current of the motor is negative.

[0079] like Figure 5 As shown, the method for inverter dead zone compensation also includes: step 31, when the motor is running at medium and high frequency heavy load, the sampled current is strongly sinusoidal, and the zero point clamping has little effect on the polarity judgment. At this time, the sampled current filter can be directly judged for polarity. This process improves the real-time performance of medium and high frequency dead zone compensation. The definition of its polarity is the same as that of low frequency, that is, when the current is greater than 0, the current polarity at this time is expressed as a high level, that is, the current is positive; when the current is equal to 0, the current polarity is negative, and then step 4 is executed to perform dead zone compensation. Among them, the speed of medium and high frequency can generally be selected as more than 20% of the rated speed, and the threshold is actually selected according to the test conditions.

[0080] In the solution of the present invention, when the medium and high frequency heavy load current is large, the sampled current itself has a high sinusoidal degree, and the polarity is directly judged based on the sampled current, which reduces the complexity of large current calculation and improves the real-time performance of dead zone compensation.

[0081] At step S140, according to the polarity of the three-phase current of the motor, the on-time of the switch tube of the upper bridge arm and the on-time of the switch tube of the lower bridge arm of each phase bridge arm in the three-phase bridge arm are adjusted to compensate for the dead zone of the inverter.

[0082] The dead zone compensation scheme for the inverter proposed in the scheme of the present invention is to judge the current polarity on the basis of vector control, and the judgment of the current polarity is segmented according to the threshold value set in advance, and then the dead zone effect is compensated according to the current polarity, and the dead zone compensation can be realized on the original hardware without additional circuits. In the scheme of the present invention, the polarity is judged by the main component of the current, and compensation is performed according to the current polarity. The threshold segmented compensation is set according to the size of the feedback current, which improves the torque pulsation, current distortion, noise and other problems caused by the dead zone effect of the inverter, ensures the accuracy and reliability of the compensation for the dead zone effect of the inverter, and allows the switch tube to reach the ideal switching state as much as possible.

[0083] In some embodiments, the polarity of the three-phase current of the motor includes: the current polarity of any phase current of the three-phase current of the motor is positive, or the current polarity of any phase current of the three-phase current of the motor is negative. In step S140, according to the polarity of the three-phase current of the motor, the conduction time of the switch tube of the upper bridge arm of each phase bridge arm in the three-phase bridge arm and the conduction time of the switch tube of the lower bridge arm are adjusted to compensate the dead zone of the inverter, including any of the following adjustment situations:

[0084] The first adjustment scenario: for any phase current among the three-phase current of the motor, if the current polarity of any phase current is positive, then for any phase bridge arm corresponding to the any phase current in the inverter, the conduction time of the switch tube of the upper bridge arm in the any phase bridge arm is extended by a set time, and the conduction time of the switch tube of the lower bridge arm in the any phase bridge arm is shortened by a set time.

[0085] The second adjustment scenario: for any phase current among the three-phase current of the motor, if the current polarity of any phase current is negative, then for any phase bridge arm corresponding to the any phase current in the inverter, the conduction time of the switch tube of the upper bridge arm in the any phase bridge arm is shortened by a set time, and the conduction time of the switch tube of the lower bridge arm in the any phase bridge arm is extended by a set time.

[0086] like Figure 5 As shown, the inverter dead zone compensation method also includes: step 4, when the polarity is determined, the specific compensation method is: i>0, the corresponding upper tube PWM ideal conduction time is extended by Td, and the corresponding lower tube PWM conduction time is shortened by Td, so that the actual and ideal are the same, and the dead zone compensation is completed; i<0, the opposite is true. Among them, the selection of time Td needs to comprehensively consider the selected inverter characteristics and the program preset dead zone time, and finally ensure that the compensated drive waveform is as ideal as possible.

[0087] Figure 7 The figure is a schematic diagram of the current flow between the inverter and one phase of the motor (such as phase A). Fig. 9 Schematic diagram of the curve of the ideal switch and the actual switch signal of a bridge arm of the inverter (such as the bridge arm composed of switch S1 and switch S4). Figure 7 In the current flow diagram shown, i>0, the lower bridge diode D4 continues the current, the upper bridge switch tube S1 outputs a positive pulse that is Td shorter than the ideal, while the lower bridge switch tube S4 extends Td compared to the ideal; see Fig. 9 In the example shown, during compensation, the conduction time of the upper tube is extended by Td, and the corresponding lower tube is shortened by Td, so that the actual and ideal are the same; i<0, the opposite is true.

[0088] In the scheme of the present invention, the operating frequency of the motor is divided according to the three-phase current of the motor. When the motor is at low frequency, light load and small current, the converted DC is filtered for current polarity detection. The fundamental wave restored after filtering is directly used for current polarity detection, which can improve the accuracy of current polarity judgment and reduce interference, and ensure that the dead zone compensation is accurate and reliable. When the motor is at medium and high frequency, heavy load and large current, the sampled current itself has a high sinusoidality, and the polarity is directly judged based on the sampled current, which reduces the complexity of large current calculation and improves the real-time performance of dead zone compensation.

[0089] The technical solution of this embodiment is adopted, through the dead zone compensation of the three-phase full-bridge inverter in the frequency converter of the motor, the three-phase current of the motor is used, and whether the motor is running at low frequency and light load or medium and high frequency and heavy load is determined according to the three-phase current of the motor. When the motor is running at low frequency and light load, the three-phase current of the motor is transformed and the current polarity is judged. When the motor is running at medium and high frequency and heavy load, the polarity is judged according to the three-phase current of the motor. According to the polarity of a phase current in the determined three-phase current, the conduction time of the upper and lower switch tubes of a phase bridge arm in the three-phase full-bridge inverter corresponding to the phase current is extended or shortened to realize the compensation of the dead time of certain bridge arms; thus, by judging the current polarity on the basis of vector control and compensating for the dead zone effect according to the current polarity, the accuracy and reliability of the dead zone effect compensation of the inverter are guaranteed.

[0090] According to an embodiment of the present invention, a control device for an inverter corresponding to the control method for the inverter is also provided. Figure 4 The schematic diagram of the structure of an embodiment of the device of the present invention is shown. The inverter comprises: a three-phase bridge arm; each bridge arm of the three-phase bridge arm comprises: a switch tube of an upper bridge arm and a switch tube of a lower bridge arm; the midpoint of each bridge arm is connected to the winding of the corresponding phase in the three-phase winding of the motor. Figure 6 Figure 1 is a schematic diagram of the structure of the inverter and the motor. Figure 6As shown, the structure of the inverter and the motor includes: capacitor C1, capacitor C2, switch tube S1, freewheeling diode D1 of switch tube S1, switch tube S2, freewheeling diode D2 of switch tube S2, switch tube S3, freewheeling diode D3 of switch tube S3, switch tube S4, freewheeling diode D4 of switch tube S4, switch tube S5, freewheeling diode D5 of switch tube S5, switch tube S6, freewheeling diode D6 of switch tube S6, and three-phase winding of motor MO. The collector of the switch tube S1 is connected to the cathode of the diode D1, and the emitter of the switch tube S1 is connected to the anode of the diode D1; the collector of the switch tube S2 is connected to the cathode of the diode D2, and the emitter of the switch tube S2 is connected to the anode of the diode D2; the collector of the switch tube S3 is connected to the cathode of the diode D3, and the emitter of the switch tube S3 is connected to the anode of the diode D3; the collector of the switch tube S4 is connected to the cathode of the diode D4, and the emitter of the switch tube S4 is connected to the anode of the diode D4; the collector of the switch tube S5 is connected to the cathode of the diode D5, and the emitter of the switch tube S5 is connected to the anode of the diode D5; the collector of the switch tube S6 is connected to the cathode of the diode D6, and the emitter of the switch tube S6 is connected to the anode of the diode D6. Among them, the positive end of the DC bus voltage Udc is respectively connected to the positive electrode of capacitor C1, the collector of switch tube S1, the collector of switch tube S3, and the collector of switch tube S5; the negative electrode of capacitor C1 is connected to the positive electrode of capacitor C2 and both are grounded (i.e., connected to the zero point). The negative end of the DC bus voltage Udc is connected to the negative electrode of capacitor C2, the emitter of switch tube S4, the emitter of switch tube S6, and the emitter of switch tube S2. The emitter of switch tube S1 is connected to the collector of switch tube S4, and is connected to the first phase (such as phase A) of the three-phase winding of the motor; the emitter of switch tube S3 is connected to the collector of switch tube S6, and is connected to the second phase (such as phase B) of the three-phase winding of the motor; the emitter of switch tube S5 is connected to the collector of switch tube S2, and is connected to the third phase (such as phase C) of the three-phase winding of the motor.

[0091] In the scheme of the present invention, Figure 4 As shown, the inverter control device includes: an acquisition unit 102 and a control unit 104.

[0092] The acquisition unit 102 is configured to acquire the three-phase current of the motor when the motor is running. The specific functions and processing of the acquisition unit 102 refer to step S110.

[0093] The control unit 104 is configured to determine the frequency interval to which the operating frequency of the motor belongs within the set frequency range according to the three-phase current of the motor. The specific functions and processing of the control unit 104 refer to step S120.

[0094] In some embodiments, the set frequency range includes: a first frequency interval and a second frequency interval, the upper limit of the first frequency interval is less than the lower limit of the second frequency interval, the first frequency interval is such as a low-frequency light-load interval, and the second frequency interval is such as a medium-high frequency heavy-load interval. The control unit 104 determines the frequency interval to which the operating frequency of the motor belongs within the set frequency range according to the three-phase current of the motor, including:

[0095] The control unit 104 is further configured to determine whether any phase current of the three-phase current of the motor is less than a preset current threshold value. The current of any phase of the three-phase current of the motor, such as the sampled current i_samp; the preset current threshold value, such as the current threshold value i_threshold. The specific functions and processing of the control unit 104 are also referred to step S210.

[0096] The control unit 104 is further configured to determine that the operating frequency of the motor is in the first frequency range if it is determined that any phase current is less than a preset current threshold. The specific functions and processing of the control unit 104 are also shown in step S220.

[0097] The control unit 104 is further configured to determine that the operating frequency of the motor is in the second frequency range if it is determined that any phase current is greater than or equal to a preset current threshold. The specific functions and processing of the control unit 104 are also shown in step S230.

[0098] Figure 5 FIG. 1 is a flow chart of a method for inverter dead zone compensation according to the present invention. Figure 5 As shown, a method for inverter dead zone compensation includes:

[0099] Step 1, obtain the three-phase current of the motor as the sampling current i_samp; the sampling current first performs a preset value judgment, that is, judges whether the sampling current i_samp<current threshold i_threshold: if so, execute step 2, otherwise execute step 3.

[0100] Step 2: When the sampling current i_samp<current threshold i_threshold, that is, when the motor is running at low frequency and light load, step 21 is executed, that is, the polarity is determined by coordinate transformation, and then dead zone compensation is performed.

[0101] Step 3: When the sampling current i_samp≥current threshold i_threshold is satisfied, that is, when the motor is running at a medium or high frequency, step 31 is executed, that is, the sampling current can be directly used to determine the polarity, and then dead zone compensation is performed.

[0102] In the scheme of the present invention, dead zone compensation is performed on the basis of coordinate transformation, and the dead zone compensation is processed in segments according to the current size. When the current is small, the main component of the current is used to judge the polarity, and after the current becomes larger, the measured current is directly used to judge the polarity. This segmented processing well solves the problems of zero point clamping and complex large current calculation when judging the polarity of small currents, improves the accuracy of current polarity judgment, and ensures the accuracy and reliability of dead zone effect compensation for the inverter.

[0103] The control unit 104 is further configured to determine the polarity of the three-phase current of the motor according to the frequency interval to which the running frequency of the motor belongs within the set frequency range. The specific functions and processing of the control unit 104 are also shown in step S130.

[0104] In some embodiments, the set frequency range includes: a first frequency interval and a second frequency interval, the upper limit of the first frequency interval is less than the lower limit of the second frequency interval, the first frequency interval is such as a low-frequency light-load interval, and the second frequency interval is such as a medium-high frequency heavy-load interval. The control unit 104 determines the polarity of the three-phase current of the motor according to the frequency interval to which the operating frequency of the motor belongs within the set frequency range, including any of the following polarity determination situations:

[0105] The first polarity determination scenario: the control unit 104 is further specifically configured to obtain a first processed value of the three-phase current of the motor after coordinate transformation and filtering of the three-phase current of the motor if the operating frequency of the motor is in the first frequency range; and then, determine the polarity of the three-phase current of the motor according to the first processed value of the three-phase current of the motor.

[0106] In some implementations, the control unit 104 performs coordinate transformation and filtering on the three-phase current of the motor to obtain a first processed value of the three-phase current of the motor, including:

[0107] The control unit 104 is further configured to convert the three-phase current of the motor from the abc coordinate system to the αβ coordinate system and then to the dq coordinate system. The specific functions and processing of the control unit 104 are also shown in step S310.

[0108] The control unit 104 is further configured to perform filtering processing in the dq coordinate system, and then perform inverse transformation to restore to the abc coordinate system to obtain the first processed value of the three-phase current of the motor. The specific functions and processing of the control unit 104 are also shown in step S320.

[0109] like Figure 5As shown, the method for inverter dead zone compensation also includes: step 21, considering that when the motor runs at low frequency and light load, the current is small and due to the influence of zero point clamping, the current directly sampled is not an ideal sinusoidal current. According to Fourier analysis, the current directly sampled is composed of fundamental component and harmonic component. If the current polarity is directly judged by the sampled current, it will cause polarity deviation and cannot improve the current distortion caused by the inverter dead zone effect; and directly using the sampled current for sector judgment will also bring errors to the sector judgment. For this reason, most methods are to directly filter the sampled current, but this will cause errors in the amplitude and phase of the sampled current. If the fundamental and harmonic waves of the sampled current are separated, the accuracy will be improved by using the fundamental wave containing the main information for processing.

[0110] Therefore, the solution of the present invention adopts this decomposition idea, performs forward transformation on the three-phase current, filters the three-phase current in the dq coordinate system, restores the three-phase current by reverse transformation, and then executes step 4 to perform dead zone compensation.

[0111] Specifically, in step 21, the sampled current is first transformed from the abc coordinate system to the two-phase stationary coordinate system αβ, and then to the dq coordinate system. a 、i b 、i c In the abc coordinate system and the αβ coordinate system, it is expressed as AC, but when converted to the dq coordinate system, the corresponding variable is expressed as DC. The DC filtering process will not affect its amplitude and phase. The original current converted to the dq coordinate system contains the fundamental component and harmonic component of the original current signal, which can be expressed as follows (1):

[0112]

[0113] Among them, i bd 、i bq It is the DC component in the synchronously rotating dq coordinate system, which is obtained by converting the fundamental wave component in the abc coordinate system. hd 、i hq It is the high-order harmonic component in the synchronously rotating dq coordinate system, which is obtained by converting the high-frequency component in the abc coordinate system. d , q-axis current i q Filtering is performed to remove the high-frequency components in the current signal. The filtered current is the DC component obtained by converting the fundamental component of the original current, which contains the main components of the original current. The filtered DC component is then restored to the abc coordinate system through inverse transformation using equations (2) and (3), where θ is i bd and i AThe angle between the current and the motor current is determined by the current in the abc coordinates. The accuracy of the current polarity determination is improved by the determination of the current polarity through coordinate transformation. Compared with directly filtering the sampled current, the current polarity determination through coordinate transformation converts the current to a DC state for filtering. The DC component will not change its amplitude and phase through filtering, which greatly improves the accuracy of the current polarity determination.

[0114]

[0115]

[0116] The three-phase current obtained by transforming equations (2) and (3) is:

[0117]

[0118] Among them, i α is the α-axis current, i β is the β-axis current. Afterwards, the polarity of the current converted to the abc coordinate system is determined.

[0119] In the scheme of the present invention, when the motor is at low frequency, light load and small current, due to the existence of zero-crossing clamping, filtering the converted DC will not change the amplitude and phase of the original signal. The filtered current is inversely transformed and restored to the original. The restored signal reduces high-frequency interference and retains useful components compared to the original signal. Compared with directly judging the sampled current, this method improves the accuracy of filtering out interference and greatly improves the accuracy of current polarity judgment.

[0120] In some embodiments, the control unit 104 determines the polarity of the three-phase current of the motor based on the first processed value of the three-phase current of the motor, including: the control unit 104 is specifically configured to determine whether the first processed value of any phase current among the first processed values ​​of the three-phase current of the motor is greater than 0: if so, determine that the current polarity of any phase current of the three-phase current of the motor is positive; otherwise, determine that the current polarity of any phase current of the three-phase current of the motor is negative.

[0121] like Figure 5 As shown, the method for inverter dead zone compensation also includes: in step 21, the polarity of the current converted to the abc coordinate system is judged, and it is defined that when the current is greater than 0, the current polarity at this time is represented as a high level, that is, the current is positive; when the current is equal to 0, the current polarity is negative. The relationship between the current waveform of a phase of the motor and its polarity change over time can be seen in Figure 8 The example shown, Figure 8 It is a schematic diagram of a curve showing the current waveform of one phase (such as phase B) of the motor and its polarity changing with time.

[0122] In the scheme of the present invention, when the motor is at low frequency, light load and small current, the current polarity is judged by using the zero crossing point of the sinusoidal current after conversion, thereby improving the accuracy of the current polarity judgment and reducing interference, and ensuring that the dead zone compensation is accurate and reliable.

[0123] The second polarity determination scenario: the control unit 104 is further configured to determine the polarity of the three-phase current of the motor according to the current value of the three-phase current of the motor if the operating frequency of the motor is in the second frequency range; or, after filtering the three-phase current of the motor, obtain a second processed value of the three-phase current of the motor; and then, determine the polarity of the three-phase current of the motor according to the second processed value of the three-phase current of the motor.

[0124] In the scheme of the present invention, when the motor is at low frequency, light load and small current, due to the existence of zero-crossing clamping, filtering the converted DC will not change the amplitude and phase of the original signal. The filtered current is reversely transformed and restored to the original. Compared with the original signal, the restored signal reduces high-frequency interference and retains useful components. Compared with directly judging the sampled current, this method improves the accuracy of filtering out interference; when the motor is at medium and high frequency, heavy load and large current, there is no zero-crossing clamping, and the sampled current does not need to be transformed, and the polarity of the sampled current can be directly judged, reducing the complexity of large current polarity judgment and improving the real-time performance of polarity judgment.

[0125] In the solution of the present invention, the current signal can be filtered at any stage of the current, which can improve the accuracy of polarity judgment and better achieve dead zone compensation; the cutoff frequency of the filter can be determined according to the actual loop bandwidth.

[0126] In some embodiments, the control unit 104 determines the polarity of the three-phase current of the motor according to the current value of the three-phase current of the motor, including: the control unit 104 is specifically configured to determine whether the current value of any phase current among the current values ​​of the three-phase current of the motor is greater than 0: if so, determine that the current polarity of any phase current of the three-phase current of the motor is positive; otherwise, determine that the current polarity of any phase current of the three-phase current of the motor is negative.

[0127] Alternatively, the control unit 104 determines the polarity of the three-phase current of the motor according to the second processed value of the three-phase current of the motor, including: the control unit 104 is specifically configured to determine whether the second processed value of any phase current among the second processed values ​​of the three-phase current of the motor is greater than 0: if so, determine that the current polarity of any phase current of the three-phase current of the motor is positive; otherwise, determine that the current polarity of any phase current of the three-phase current of the motor is negative.

[0128] like Figure 5 As shown, the method for inverter dead zone compensation also includes: step 31, when the motor is running at medium and high frequency heavy load, the sampled current is strongly sinusoidal, and the zero point clamping has little effect on the polarity judgment. At this time, the sampled current filter can be directly judged for polarity. This process improves the real-time performance of medium and high frequency dead zone compensation. The definition of its polarity is the same as that of low frequency, that is, when the current is greater than 0, the current polarity at this time is expressed as a high level, that is, the current is positive; when the current is equal to 0, the current polarity is negative, and then step 4 is executed to perform dead zone compensation. Among them, the speed of medium and high frequency can generally be selected as more than 20% of the rated speed, and the threshold is actually selected according to the test conditions.

[0129] In the solution of the present invention, when the medium and high frequency heavy load current is large, the sampled current itself has a high sinusoidal degree, and the polarity is directly judged based on the sampled current, which reduces the complexity of large current calculation and improves the real-time performance of dead zone compensation.

[0130] The control unit 104 is further configured to adjust the on-time of the switch tube of the upper bridge arm and the on-time of the switch tube of the lower bridge arm of each phase bridge arm in the three-phase bridge arm according to the polarity of the three-phase current of the motor, so as to compensate the dead zone of the inverter. The specific functions and processing of the control unit 104 are also shown in step S140.

[0131] The dead zone compensation scheme for the inverter proposed in the scheme of the present invention is to judge the current polarity on the basis of vector control, and the judgment of the current polarity is segmented according to the threshold value set in advance, and then the dead zone effect is compensated according to the current polarity, and the dead zone compensation can be realized on the original hardware without additional circuits. In the scheme of the present invention, the polarity is judged by the main component of the current, and compensation is performed according to the current polarity. The threshold segmented compensation is set according to the size of the feedback current, which improves the torque pulsation, current distortion, noise and other problems caused by the dead zone effect of the inverter, ensures the accuracy and reliability of the compensation for the dead zone effect of the inverter, and allows the switch tube to reach the ideal switching state as much as possible.

[0132] In some embodiments, the polarity of the three-phase current of the motor includes: the current polarity of any phase current of the three-phase current of the motor is positive, or the current polarity of any phase current of the three-phase current of the motor is negative. The control unit 104 adjusts the conduction time of the switch tube of the upper bridge arm of each phase bridge arm in the three-phase bridge arm and the conduction time of the switch tube of the lower bridge arm according to the polarity of the three-phase current of the motor to compensate for the dead zone of the inverter, including any of the following adjustment situations:

[0133] The first adjustment scenario: the control unit 104 is specifically configured to, for any phase current among the three-phase current of the motor, if the current polarity of any phase current is positive, then for any phase bridge arm corresponding to the any phase current in the inverter, the conduction time of the switch tube in the upper bridge arm of any phase bridge arm is extended by a set time, and the conduction time of the switch tube in the lower bridge arm of any phase bridge arm is shortened by a set time.

[0134] The second adjustment scenario: the control unit 104 is specifically configured to, for any phase current among the three-phase currents of the motor, if the current polarity of any phase current is negative, then for any phase bridge arm in the inverter corresponding to the any phase current, the conduction time of the switch tube in the upper bridge arm of any phase bridge arm is shortened by a set time, and the conduction time of the switch tube in the lower bridge arm of any phase bridge arm is extended by a set time.

[0135] like Figure 5 As shown, the inverter dead zone compensation method also includes: step 4, when the polarity is determined, the specific compensation method is: i>0, the corresponding upper tube PWM ideal conduction time is extended by Td, and the corresponding lower tube PWM conduction time is shortened by Td, so that the actual and ideal are the same, and the dead zone compensation is completed; i<0, the opposite is true.

[0136] Figure 7 The figure is a schematic diagram of the current flow between the inverter and one phase of the motor (such as phase A). Fig. 9 Schematic diagram of the curve of the ideal switch and the actual switch signal of a bridge arm of the inverter (such as the bridge arm composed of switch S1 and switch S4). Figure 7 In the current flow diagram shown, i>0, the lower bridge diode D4 continues the current, the upper bridge switch tube S1 outputs a positive pulse that is Td shorter than the ideal, while the lower bridge switch tube S4 extends Td compared to the ideal; see Fig. 9 In the example shown, during compensation, the conduction time of the upper tube is extended by Td, and the corresponding lower tube is shortened by Td, so that the actual and ideal are the same; i<0, the opposite is true.

[0137] In the scheme of the present invention, the operating frequency of the motor is divided according to the three-phase current of the motor. When the motor is at low frequency, light load and small current, the converted DC is filtered for current polarity detection. The fundamental wave restored after filtering is directly used for current polarity detection, which can improve the accuracy of current polarity judgment and reduce interference, and ensure that the dead zone compensation is accurate and reliable. When the motor is at medium and high frequency, heavy load and large current, the sampled current itself has a high sinusoidality, and the polarity is directly judged based on the sampled current, which reduces the complexity of large current calculation and improves the real-time performance of dead zone compensation.

[0138] Since the processing and functions implemented by the device of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned method, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be made here.

[0139] According to an embodiment of the present invention, a frequency converter corresponding to the control device of the inverter is also provided. The frequency converter may include: the control device of the inverter described above.

[0140] Since the processing and functions implemented by the frequency converter of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned devices, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be made here.

[0141] According to an embodiment of the present invention, a motor corresponding to the control device of the inverter is also provided. The motor may include: the control device of the inverter described above, or the frequency converter described above.

[0142] Since the processing and functions implemented by the motor of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned device, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0143] According to an embodiment of the present invention, a computer program product corresponding to the inverter control method is also provided, including a computer program, and when the computer program is executed by a processor, the steps of the inverter control method described above are implemented.

[0144] Since the processing and functions implemented by the product of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned inverter and motor, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be made here.

[0145] According to an embodiment of the present invention, a storage medium corresponding to the inverter control method is also provided, wherein the storage medium includes a stored program, wherein when the program is executed, the device where the storage medium is located is controlled to execute the steps of the inverter control method described above.

[0146] Since the processing and functions implemented by the storage medium of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned method, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be made here.

[0147] In summary, it is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0148] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims

1. A control method for an inverter, characterized in that: The inverter comprises: a three-phase bridge arm; each phase bridge arm of the three-phase bridge arm comprises: a switch tube of an upper bridge arm and a switch tube of a lower bridge arm; the midpoint of each phase bridge arm is connected to the winding of the corresponding phase in the three-phase winding of the motor; the control method of the inverter comprises: When the motor is running, obtaining the three-phase current of the motor; Determining, according to the three-phase current of the motor, a frequency interval to which the operating frequency of the motor belongs within a set frequency range; Determining the polarity of the three-phase current of the motor according to the frequency interval to which the operating frequency of the motor belongs within the set frequency range; According to the polarity of the three-phase current of the motor, the conduction time of the switch tube of the upper bridge arm and the conduction time of the switch tube of the lower bridge arm of each phase bridge arm in the three-phase bridge arm are adjusted to compensate the dead zone of the inverter.

2. The inverter control method according to claim 1, characterized in that: Setting a frequency range, including: a first frequency interval and a second frequency interval, wherein an upper limit of the first frequency interval is less than a lower limit of the second frequency interval; Determining, according to the three-phase current of the motor, a frequency interval to which the operating frequency of the motor belongs within a set frequency range, comprising: For any phase current of the three-phase current of the motor, determining whether the any phase current is less than a preset current threshold; If it is determined that any phase current is less than a preset current threshold, determining that the operating frequency of the motor is in a first frequency interval; If it is determined that any phase current is greater than or equal to a preset current threshold, it is determined that the operating frequency of the motor is in a second frequency interval.

3. The inverter control method according to claim 1, characterized in that: Setting a frequency range, including: a first frequency interval and a second frequency interval, wherein an upper limit of the first frequency interval is less than a lower limit of the second frequency interval; Determining the polarity of the three-phase current of the motor according to the frequency interval to which the operating frequency of the motor belongs within the set frequency range includes: If the operating frequency of the motor is in the first frequency interval, coordinate transformation and filtering are performed on the three-phase current of the motor to obtain a first processed value of the three-phase current of the motor; then, the polarity of the three-phase current of the motor is determined according to the first processed value of the three-phase current of the motor; If the operating frequency of the motor is in the second frequency range, the polarity of the three-phase current of the motor is determined according to the current value of the three-phase current of the motor; or, the three-phase current of the motor is filtered to obtain a second processed value of the three-phase current of the motor; then, the polarity of the three-phase current of the motor is determined according to the second processed value of the three-phase current of the motor.

4. The control method of the inverter according to claim 3, characterized in that: After coordinate transformation and filtering are performed on the three-phase current of the motor, a first processed value of the three-phase current of the motor is obtained, including: The three-phase current of the motor is converted from the abc coordinate system to the αβ coordinate system, and then to the dq coordinate system; The filtering process is performed in the dq coordinate system, and then the inverse transformation is restored to the abc coordinate system to obtain the first processed value of the three-phase current of the motor.

5. The control method of the inverter according to claim 3, characterized in that: in, Determining the polarity of the three-phase current of the motor according to the first processed value of the three-phase current of the motor includes: For the first processed value of any phase current among the first processed values ​​of the three-phase current of the motor, determine whether the first processed value of any phase current is greater than 0: if so, determine that the current polarity of any phase current of the three-phase current of the motor is positive; otherwise, determine that the current polarity of any phase current of the three-phase current of the motor is negative; and / or, Determining the polarity of the three-phase current of the motor according to the current value of the three-phase current of the motor includes: For the current value of any phase current among the current values ​​of the three-phase current of the motor, determine whether the current value of any phase current is greater than 0: if so, determine that the current polarity of any phase current of the three-phase current of the motor is positive; otherwise, determine that the current polarity of any phase current of the three-phase current of the motor is negative; And / or, determining the polarity of the three-phase current of the motor according to the second processed value of the three-phase current of the motor, comprising: For the second processed value of any phase current among the second processed values ​​of the three-phase current of the motor, determine whether the second processed value of any phase current is greater than 0: if so, determine that the current polarity of any phase current of the three-phase current of the motor is positive; otherwise, determine that the current polarity of any phase current of the three-phase current of the motor is negative.

6. The inverter control method according to any one of claims 1 to 5, characterized in that: The polarity of the three-phase current of the motor includes: the current polarity of any phase current of the three-phase current of the motor is positive, or the current polarity of any phase current of the three-phase current of the motor is negative; According to the polarity of the three-phase current of the motor, the on-time of the switch tube of the upper bridge arm and the on-time of the switch tube of the lower bridge arm of each phase bridge arm in the three-phase bridge arm are adjusted to perform dead zone compensation on the inverter, including: For any phase current among the three-phase currents of the motor, if the current polarity of any phase current is positive, for any phase bridge arm corresponding to the any phase current in the inverter, the on-time of the switch tube of the upper bridge arm in the any phase bridge arm is extended by a set time, and the on-time of the switch tube of the lower bridge arm in the any phase bridge arm is shortened by a set time; For any phase current among the three-phase currents of the motor, if the current polarity of any phase current is negative, then for any phase bridge arm corresponding to the any phase current in the inverter, the conduction time of the switch tube of the upper bridge arm in the any phase bridge arm is shortened by a set time, and the conduction time of the switch tube of the lower bridge arm in the any phase bridge arm is extended by a set time.

7. A control device for an inverter, characterized in that: The inverter comprises: a three-phase bridge arm; each phase bridge arm of the three-phase bridge arm comprises: a switch tube of an upper bridge arm and a switch tube of a lower bridge arm; the midpoint of each phase bridge arm is connected to the winding of the corresponding phase in the three-phase winding of the motor; the control device of the inverter comprises: an acquisition unit, configured to acquire the three-phase current of the motor when the motor is running; A control unit, configured to determine a frequency interval within a set frequency range to which the operating frequency of the motor belongs according to the three-phase current of the motor; The control unit is further configured to determine the polarity of the three-phase current of the motor according to the frequency interval to which the operating frequency of the motor belongs within the set frequency range; The control unit is also configured to adjust the conduction time of the switch tube of the upper bridge arm and the conduction time of the switch tube of the lower bridge arm of each phase bridge arm in the three-phase bridge arm according to the polarity of the three-phase current of the motor, so as to compensate for the dead zone of the inverter.

8. A frequency converter, characterized in that: include: The inverter control device as claimed in claim 7.

9. A motor, characterized in that: include: The control device of the inverter as claimed in claim 7, or the frequency converter as claimed in claim 8.

10. A storage medium, characterized in that: The storage medium includes a stored program, wherein when the program is executed, the device where the storage medium is located is controlled to execute the inverter control method according to any one of claims 1 to 6.

11. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the inverter control method according to any one of claims 1 to 6 are implemented.

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